Aortic dissection

Dr Prakash Sapkale

• Aortic dissection is a longitudinal split or partition in the media of the aorta.

• Life threatening medical emergency• Common in 50-70 age group

• Pathophysiology:– Classic aortic dissection: the initial

event was log thought to be an intimal tear->extravasation of blood into the media->extension of dissection from point of dissection.• Demonstration of intimal flap was

considered necessary for diagnosis– Aortic intramural

hematoma:degeneration of media->rupture of vasa vasorum->bleeding into media->linear extension of the hematoma within the aortic wall->may heal or there may be rupture into the aortic lumen.• Occurs in 25%

• Mortality/Morbidity:

– Mortality in untreated aortic dissection is 1% per hour for first 48 hrs rising to 80% in 2 weeks

– Operative mortality is considerable– Occlusion of aortic branch vessels from aortic dissection may result in stroke,

renal failure, mesenteric ischemia, lower extremity ischemia, and paraplegia (caused by obstruction of the spinal artery).

– Occlusion of aortic branch vessels from aortic dissection may result in stroke, renal failure, mesenteric ischemia, lower extremity ischemia, and paraplegia (caused by obstruction of the spinal artery).

– aortic intramural hematoma is rarely associated with significant narrowing of aortic branch vessels.

• Type A mortality 1-2% per hour after onset of symptoms, total up to 90% non-treated, 40% when treated.

• 1 year survival Type B up to 85% if medically treated (5 year > 70%)

• Risk factors:– Chronic hypertension ,Connective tissue disorders (Marfan syndrome, rare in

Ehlers-Danlos syndrome) ,Bicuspid aortic valve ,Coarctation of the aorta ,Turner syndrome ,Takayasu arteritis ,Giant cell arteritis ,Pregnancy, Trauma ,Crack cocaine use ,Cardiac catheterization ,Metabolic disorders

– Sex: Aortic dissections are more common in men than in women (ratio, 3:1)

• Clinical features:– Ripping or tearing pain in the interscapular area ,Abrupt onset of the

pain ,Acute, severe chest pain (Anterior chest pain can mimic acute myocardial infarction) ,Pain extending to the neck or jaw ,Altered mental status ,Cerebrovascular accident symptoms ,Syncope ,Limb paresthesias ,Horner syndrome ,Dyspnea ,Dysphagia ,Flank pain if the renal arteries are involved ,Hypertension ,Hypotension if associated with cardiac tamponade, hypovolemia, excessive vagal tone

classification• Stanford classification:( important for

treatment)

– Type A: The ascending aorta is involved. – Type B: The descending aorta is

involved.

• DeBakey classification (now replaced by stanford classification)

– Type I: The entire aorta is involved. – Type II: Only the ascending aorta is

involved. – Type III: Only the descending aorta is

involved. • Type IIIA involves the descending aorta

as far as the diaphragm. • Type IIIB involves the descending aorta

below the diaphragm.

Imaging modalities

• MRI has high sensitivity and specificity but not useful in unstable patients

• CT scan• Transoesophageal echocardiography

radiograph• All findings on plain images are nonspecific but may help in determining the need

for further workup.

• Mediastinal widening (most common plain radiographic finding in aortic dissection, noted in 80% of patients) (see Image 2)

• Double aortic knob sign (in 40% of patients) • Diffuse enlargement of the aorta with poor definition or irregularity of the aortic

contour • Inward displacement of aortic wall calcification of more than 10 mm • Tracheal displacement to the right • Pleural effusion (more common on the left side, suggests leakage) • Pericardial effusion • Cardiac enlargement • Displacement of a nasogastric tube • Left apical opacity

Aortic dissection

CT Scan• The sensitivity of CT is 87-94%, and the specificity is 92-100%.• scanning is performed from the thoracic inlet to the common femoral arteries

• nonenhanced CT -diagnosis of acute hemorrhage and aortic rupture• 25-30 seconds after the injection of contrast material. Nonionic contrast material (120-135 mL) at a

rate of 3-4 mL/s– test injection of contrast -to determine circulation time or an automated bolus detection scheme. one may

visually differentiate the true and false lumen based on contrast arrival time.• delayed images of the false lumen and aortic branches.

• CT findings =• Aortic intramural hematoma: Crescentic high-attenuating clot within the media, with internally

displaced calcification • Intimal flap separating the two aortic channels • Hemorrhagic pleural and pericardial effusions and mediastinal hemorrhage may be seen. • postoperative follow-up to depict associated complications:

– Thrombosis ,Hemorrhage ,Infection ,Pseudoaneurysms ,Aortoenteric fistula ,Ureteral obstruction• Aortic intramural hematoma can be misinterpreted as an aneurysm with thrombus or arteritis.

• True lumen: • Surrounded by calcifications (if present) • Smaller than false lumen • Usually origin of celiac trunk, SMA and right renal artery

• False lumen: • Flow or occluded by thrombus (chronic). • Delayed enhancement• Wedges around true lumen (beak-sign)• Collageneous media-remnants (cobwebs)• Larger than true lumen• Circular configuration (persistent systolic pressure)• Outer curve of the arch• Usually origin of left renal artery• Surrounds true lumen in Type A dissection

MRI• The sensitivity and specificity are both more than 90%.unstable patients should not be studied with

MR.

• MRI findings:

• aortic dissection :• an intimal flap of medium–signal intensity surrounded by a signal void of fast-flowing blood on

(ECG)-gated spin-echo or double inversion recovery single shot fast spin-echo • With cine gradient echo imaging, the intimal flap is a dark line against the high -signal intensity of

the flowing blood and may change configuration during the cardiac cycle. Careful examination of the aortic flap during the cardiac cycle on cine MR imaging is important to detect the presence of "true lumen collapse," which may be associated with end-organ ischemia. When the intima is stripped 360° from the media and is essentially "free floating," this may result in catastrophic intimo-intimo intussusception.

• MRI findings of AIH include a crescent of blood surrounding but not compressing the aorta. The signal intensity of the crescent varies with age on T1-weighted imaging: it is isointense to muscle in the acute setting and markedly hyperintense after 3-7 days

• MRI is also helpful in postoperative follow-up for associated complications- Thrombosis, Hemorrhage , Infection, Pseudoaneurysms, Aortoenteric fistula, Ureteral obstruction

ULTRASOUND

• TEE:• sensitivity of up to 98% and a specificity of up to

97%.• ascending thoracic dissections,• cardiac tamponade, and aortic regurgitation ,

coronary arterial occlusion,

• Aortography:• Not useful in emergency setting

END